The invention relates to an apparatus for varying the position of a control device, connected to an operating element via a transmission device, that controls the output of an internal combustion engine.
With various kinds of engine regulation, such apparatus is needed for intervention into the transmission line leading from an operating element, such as a gas pedal, to a control device, such as the throttle valve of a carburetor or the adjusting lever of an injection pump, to enable influencing, i.e., varying the position of the control device as a function of various parameters. Such variations serve for instance to avoid slip between the driven wheels of a motor vehicle and the surface of the road, either during acceleration from excessive drive power, leading to so-called drive slip, or during braking from excessive engine braking moment, which leads to so-called braking slip. Such variations may also serve to limit the maximum speed of a motor vehicle independently of the gas pedal position, or to maintain a constant vehicle speed such as with a cruise control, again independently of the gas pedal position. In maximum vehicle speed limitation, the position of the control device is varied in the direction of a reduction in engine output when the desired maximum speed is reached. In constant vehicle speed regulation, the position of the control device is varied in the direction of an engine output decrease or increase, depending on whether the actual vehicle speed, detected for instance by wheel sensors, is above or below the desired constant vehicle speed.
In such apparatus, two operating states can be distinguished: first, the unregulated state, in which the position of the otherwise uninfluenced control device is controlled directly by the operating element, and second, the regulated state, in which at a predetermined position of the operating element, the control device position is varied, as compared with the control device position corresponding to the position of the operating element, by a control motor.
In a known apparatus for varying the position of a control device connected to an operating element via a transmission device and controlling the output of an internal combustion engine, the control motor can be operatively connected via a gear with a first rotary element connected to the control device, and this first rotary element is rotatably supported relative to a coaxial second rotary element connected to the operating element; the two rotary elements are prestressed by a spring, contacting one another at associated stops facing one another.
In this known apparatus, the gear is coupled with the first rotary element via a free wheel, so that upon relief of the operating element, the control device can be restored by a restoring spring, provided in the transmission device, without also rotating the gear and the rotor of the control motor in the process. This has a disadvantage that the free wheel permits adjustment of the apparatus in only one direction or rotation, and that the restoring spring must be relatively strong to overcome the unavoidable residual friction in the free wheel. Since each time the operating element is put under load both the gear and the rotor of the control motor must be rotated as well via the free wheel, the spring in the unregulated operating state, or in other words when the control motor is exerting no influence, that keeps the two rotary elements in contact with one another must be greatly reinforced, to prevent the two rotary elements from rotating apart in the unregulated operating state.